Abstract
Salinity stress affects the metabolism of plant cells leading to severe crop damage and loss of productivity. Oxidative stress is one consequence
of salinity that may be responsible for much of the damage. We investigated the immediate responses (enzymatic and non-enzymatic) to
salinity-induced oxidative stress in two major rice (Oryza sativa L.) cultivars, salt sensitive Pusa Basmati 1 (PB) and salt-tolerant Pokkali
(PK). Seedlings of both cultivars were subjected to NaCl stress (100–300 mM) for 42 h. Under NaCl stress, the salt-tolerant cv. PK showed
higher activity of the ROS scavenging enzyme, catalase (CAT) and enhanced levels of antioxidants like ascorbate (ASC) and glutathione
(GSH), than the sensitive cv. PB. Although superoxide dismutase (SOD) activity was lower in cv. PK, it showed lesser extent of membrane
damage (lipid peroxidation) and lower levels of H2O2 than cv. PB under stress. The high levels of catalase activity indicate efficient scavenging
of H2O2, which is produced more by non-enzymatic means than via SOD in cv. PK. These data indicate that concerted action of both enzymatic
and non-enzymatic ROS scavenging machineries is vital to overcome salinity-induced oxidative stress in rice.
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